Asus K73SV - Not powering on

[angelicous]

Hi there guys, i got my sisters laptop here. A friend of his tried to repair his charger by putting a new cord in, but from what i've understood, he switched the poles from it a couple of times because the laptop wasn't turning on and he thought it was that problem...

So now i have here the laptop, with the charger working ok now. I used the multimeter to measure voltage on DC jack... It's ok. Measure the round grey capacitors that are all arround on the motherboard as you see in the picture... they get to 19,5V ok, and they discharge ok if i unplug the charger.

I get some voltage readings on the battery pins as well.

But laptop has no light what so ever when plugged to the charger, and doesn't give any sign of life when pressing the power button... I've tried another charger even.

I've stripped everything but the GPU, CPU and the wifi as you can see.

I need some advice in what should i test next and what is the most likely thing that can be burn because of the switched poles on the charger. If you could point them out in the pictures that would be nice

I read that it could be a bad IC but i can't see any holes in any of them... Other than that way, i don't know how to check for a damaged IC.




greenshot

[angelicous]

Re: Asus K73SV - Not powering on

Can someone help me get the schematics first?

[dellxps15]

Re: Asus K73SV - Not powering on

dunno if it's this. check however for 3.3 volt and 5volt are present.

[angelicous]

Re: Asus K73SV - Not powering on

Hi, i guess it's not that one.

Where should i check for the 3.3 and 5volt presence?

[angelicous]

Re: Asus K73SV - Not powering on

Ok so i got a doubt. I am new to this, and i'm learning, so i was searching about mosfets. I saw that are 8 leg mosfets on the board, and if i put the multimeter on "beep" mode to check for shorts, 4 of the pins on one side would beep, and on the other side, the first pin would drain with all, the two midle ones short, and the forth one shorts with the midle ones and drains with the first.

Ok so i give it a little test and check 3 mosfets right in front of the AC jack on the top of the board. And one of them, that 1º pin that should drain with all, doesn't do nothing... Doesn't beep or drain... So this is probably a defective mosfet right?

Could this mosfet be causing the problem of the laptop not powering on?

[dellxps15]

Re: Asus K73SV - Not powering on

u see all this big coil around the board?
check voltage if present here
they are 9 coils

[angelicous]

Re: Asus K73SV - Not powering on

Only 9? I think there are 7 big ones and 4 smaller ones.

I will check the voltage. I've tested and they all short but didn't check the voltage.

[dellxps15]

Re: Asus K73SV - Not powering on

yes, sorry they are 7+4

[angelicous]

Re: Asus K73SV - Not powering on

Ok dell so i tested the voltage on the coils, and i guess they are not getting any power... I have very small readings like on the scale of 2V on the multimeter i read like 0.02 and it keeps changing, it's not stable... Sometimes goes to 1 volt, sometimes to zero...

Put one probe on each side to test right?

But as i've said before, they all "beep".

[dellxps15]

Re: Asus K73SV - Not powering on

ok so u dont have 5v and 3.3volt

beep dipend of multimeter. mine didnt beep so dunno what beep means

if beep = short then on wich one u have short?

if beep = no short then it must be something till 5v and 3.3 volt.

[angelicous]

Re: Asus K73SV - Not powering on

Sorry i don't know what you guys call this lol

This is the "beep mode" for me



It beeps when i got a short. All of them beep with the board not plugged in if i put a probe on each side of the coil

[dellxps15]

Re: Asus K73SV - Not powering on

black wire to (for example) usb metal port, red cable to one side of coil.

all beeps?

[angelicous]

Re: Asus K73SV - Not powering on

Ok, so smaller ones:
2 don't beep. 1 doesn't get any reading at all. 1 beeps.

Bigger ones:
One doesn't beep. 6 beep.

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EDIT: The one that doesn't get any reading, seams to have some values in it when i touch it. It gets 1.8 somthing, and after a second, drops to 1.

[dellxps15]

Re: Asus K73SV - Not powering on

let's wait for schematics.

edit: the one from 1.8 going to 1 is ok

[angelicous]

Re: Asus K73SV - Not powering on

Ok if it helps, here is what it's written in the board.



It says K73SD, but the model is a SV.

[angelicous]

Re: Asus K73SV - Not powering on

Well no one yet :/

Where could i search for the schematics for the board?

[angelicous]

Re: Asus K73SV - Not powering on

Ok, let me at least show you the mosfet that i think is damaged



So that 4 pins in a box, is the side that should short with each other from what i can understand.

But on other mosfets, that 1º pin on the other side, gets readings... but this one doesn't... It's like i'm not touching anything.

Could this be causing the problem alone? You can see it's very close to the DC jack

[dellxps15]

Re: Asus K73SV - Not powering on

we cant work that way trying to spot the bad part by imagination. we need proper schematics and the ic chip (qfn or so) and see the Vin pin if volt is present. if not then we need to look back, if volt is present and no volt out then we need to check for short here if not change ic.

[angelicous]

Re: Asus K73SV - Not powering on

Okey, i know.

I've been looking for schematics on google but no luck.

They aren't available for general public right?

[angelicous]

Re: Asus K73SV - Not powering on

From what i could see in these chinese website, the schematics of the models N73JQ K73SC N73JF k73SJ K73S K73E, could work too...

Here is the website:

item.taobao.com/item.htm?spm=a230r.1.14.50.tl7FXj&id=37661016801&ns=1#detail

I saw the board of the N73 and the shape is a little different but the components seem to be in the same place...

If someone could get one of those models i would apreciate it